The field of transmissions is well known, in particular concerning rotary machines and machine tools.
The most compact transmissions are generally made from one or two stages of planetary gears depending on the gear ratio that it is desired to obtain (for equal or comparable power transmission), each stage or each gear train comprising a sun gear meshing with planet gears carried by a planet carrier, which planet gears also mesh with an outer ring gear having internal teeth. The sun gear, the ring gear, and the planet carrier constitute elements of the transmission suitable for being connected externally, i.e. to the transmission line, with the gearing thus subdividing the transmission line into an upstream portion generally coming from a motor and a downstream portion which comprises a driven member of the transmission, i.e. a member that is driven at a speed of rotation applied with a given torque, this member generally also being a rotary machine (a machine tool, a roller, the screw of a press, . . . ).
The transmission also comprises an outer case containing the gearing and it too co-operates with the supports, cases, and housings of upstream and downstream portions of the transmission line. Finally, the planet carrier (or one of the planet carriers) is mounted to rotate inside the outer case by means of roll or ball bearings that require assembly or clamping means to be implemented in order to achieve axial positioning of the bearing assembly, usually under stress.
These assembly means form members that are additional to the strictly functional parts of the transmission, and constitute a factor that increases the cost price. Furthermore, such a structure requires initial assembly and needs to be monitored throughout the use of the transmission, thereby likewise constituting a drawback that needs to be remedied.
Furthermore, a manufacturer of transmissions must be capable of satisfying demand from a variety of rotary machine manufacturers that make transmission lines from components coming from a plurality of suppliers, or using components that they make themselves, depending on the machine and its shape. It is therefore necessary to make transmissions almost as custom-made items, which is not very compatible with seeking to rationalize the manufacture of transmissions in order to reduce their cost.